A Dybbuk is a Malevolent spirit from the Jewish faith. It resides in the Dybbuk box, it is believed that it is a spirit of a dislocated spirit of the dead, or a demon. The Dybbuk in the show haunted the buyers of the box until it was locked away for good. Typically, a Dybbuk will attach itself to a human host, eventually possessing and becoming one with it's host.